In the aircraft, automobile and other industries, there is an ever increasing use of plastics and fiber-reinforced composites in the fabrication of components normally made from metals or metal alloys. The conditions encountered in the environment may have a profound influence on the physical properties of polymeric materials. For example, it is known that varying degrees of humidity cause certain properties or polymers, such as creep and stress relaxation, to change to a greater or lesser extent over a period of time. It becomes important, therefore, to provide a means whereby physical properties of polymer test specimens can be determined under different environmental conditions.
It is recognized that the literature is replete with descriptions of apparatus that can be used in performing various tests on test specimens. For example, in U.S. Pat. No. 4,018,080 a device is disclosed whereby it is possible to observe the effects of stress in specimens when tensioned at cryogenic temperatures within an hermetically sealed chamber. In U.S. Pat. No. 3,350,917 the patentees disclose an environmental stress rupture apparatus which includes a means for maintaining a constant stress on a test specimen. Tubes through which a heat transfer medium is circulated are disposed adjacent to each side of the specimen. An absorbent material containing the stress environment is positioned in contact with the heating tubes and with both sides of the specimen. The only environment mentioned in the patent is a surface active agent. While the prior art test apparatus may be suitable for their intended purposes, they are generally complicated in design and often require skilled operators. Moreover, on the basis of present knowledge, none of the known apparatus is capable of measuring physical properties in different environments.
It is a principal object of this invention, therefore, to provide a test apparatus for measuring physical properties of test specimens under different environmental conditions.
Another object of the invention is to provide a device for measuring the elongation of polymeric materials or polymeric based fiber-reinforced composite materials in a moisture environment at temperatures exceeding the boiling point of water.